Temperature indicator



July 25, 1944. F. R. slAs TEMPERATURE INDICATOR Filed Nov.. 9, 1942 2 Sheets-Sheet l Freder-nck R SIas,

b5 XJ l-'hs ttor-neg July 25, 194.4. F R, slAs I 2,354,555

TEMPERATURE INDI CATOR Filed Nov. 9. 1942 2 Smets-sheet 2' An 1 A2 l A3 A4 A5 Inventor-z v Frederick R. Sies,

His Att or-neg. v

Patented July 25, 1944 assists PATENT OFFICE TEMPERATURE INDICATOR l Frederick R.. Sias, MarbleheamMass., assigner to General Electric Company, a

New York corporation o! Application November 9, 1942, Serial No. 465.0"19v Claims.

My invention relates to current responsive apparatus, and concerns particularly electrical indicating devices and systems.

It is an object oi" my invention to provide a long vscale indicator or measuring device especially adapted forindication of temperature or resistance or other quantities, or for remote position indication as in remote indicating float gauges, for example.

Another object oi' my invention iis to provide an improved circuit for an indicating system providing ambient temperature compensation and' scale angle adjustment. Claims directed to the improved circuit features described herein are contained in my divisional application Serial No. 490,347, illed June 10, 1943. v

A further object of the invention is to provide an indicator in which various desired' shapes of calibration curve may be obtained and in which a highly linear calibration curve in particular may be obtained. w

Still another object of my invention is to provide an improvedlight weight construction for e. currentresponsive device or ratio instrument itting into an unusually small space.

Other and `further objects will become ap- 'parent as the description proceeds.

In carrying out my invention in its preferred formfor the measurement of temperature I utilize a Wheatstone bridge circuit having con-` stant resistance' arms and an arm which varies in resistance in accordance with variations in temperature, and I employ a two-circuit current I responsive instrument having one winding connected as the diagonal arm or bridge balance. responsive element and having another winding so connected as to' provide a controlling torque. .In the form of my invention which I now considerthe preferred form the current responsive instrument comprises a cross coil instrument--I having the main Winding 4mechanically divided into several parts, and having the auxiliary winding mechanically divided into two parts mounted with a. magnetic axis at right angles to the magnetick axis of the main winding, having fewer? turns and having less polewidth than the main winding so as to provide a narrow magnetic field in comparison with the main winding. To cooperate with the electrical windings, I provide al permanent magnet rotor of high coercive forceY light weight magnetic material having the shape ci' a flattened right circular cylinder magnetized transversely to its axis in a direction parallel to the ilattened sides. ranged that the rotor is in its mid scale positionv The apparatus is so arwhen the magnet is in alignment with the magnetic axis of the auxiliary winding so as to give the auxiliary winding the greatest eifect upon the rotor when it is in the mid scale position.

A better understanding of my invention will be afforded by the following detailed description considered in connection with the accompanying.

drawings. and those features of the invention which are believed to be novel and patentable will be pointed out in the claims appended hereto.

In the drawings Fig. 1 is a perspective view of a cross-coil current-responsive instrument forming one embodiment of my invention: Fig. 2 is a view showing a section cut by plane' 2 2' passing through the rotor axis oi' the apparatus of Fig. 1; Fig. 3 is a perspective view, slightly enlarged, of the inner mechanism of the apparatus of Fig. 1 shown as turned 90 degrees from its position within the device as illustrated in Fig. 1;

Fig. 4 is an exploded perspective view of the mechanism of Fig. '3 with the rotor shaft and pointer shown in addition: Fig. 5 is a schematic electric circuit diagram for one embodiment of my invention for measuring temperature; Fig. 5A is a schematic diagram lexplaining the prini ciple of operation of the apparatus lof Fig. 5; Fig. 5B is a fragmentary diagram of a modiilcation in the arrangement of Fig. 5;. Fig. 6 is a circuit diagram of a modification in the arrangement of Fig. 5 utilizing a simplified circuit: Fig. 7

is a schematic circuit diagram illustrating a circuit for a resistance type temperature measuring system which is especially well adapted for an instrument of the type illustrated in Figs.- 1 to 4; Fig. 8 is a vector diagram explanatory of the principle of `operation of the apparatus of Fig. 7 and the manner inwhichtemperature compen- 4sation is obtained; and Fig. 9 is a vector diagram explanatory of the principle of operation ofthe instrument illustrated in Figs. 1 to 4 and showing thel manner in whichlinear scale calibration is obtained. Like reference characters are used ythroughout the drawings to designate like parts.

Wheatstone bridge circuits may be utilized for the measurement of temperature if one of the arms of the bridge is composed of resistance material with an appreciable temperature coemcient of resistance in comparison with other arms of the bridge. A single coil instrument, such as a galvanometer or a milliammeter, may be 'connected in the diagonal arm of the bridge and variations in temperature will cause variations in the condition of balance or extent of` unbalance ofthe bridge so as to produce variations in `current and, consequently, deflection of the instrument in response to variations in temperature. A

'I'he effect of variations in voltage oi the current source for energizing the bridge may be overcome or minimized by using a ratio type of instrument or cross-coil instrument having a main winding responsive to the condition of balance of the bridge and an auxiliary winding connected to the current source. I have found that an improved long scale indicating system with the pointer scale approximating 150 degrees may.

cuits consists of resistors II, I2, I3 and Il connected in series parallel to a source of energize.- tion current such as a battery I5 with input terminals IE and I1 serving as the energizing terminals oi the bridge and terminals IB and I9 serving as the conjugate terminals of the bridge across which the diagonal arm may be connected. The diagonal arm consists of a coil A which forms one of the windings of a cross coil current responsive instrument. The second bridge has two arms in common with the rst bridge and comprises, in addition to the resistors i2 and I4, a second'pairof resistors 20 and 2| connected in series between the energizing terminals I6 and I1 which are common to the iirst bridge and are connected to the battery I5. The conjugate terminals of the second bridge consist of the terminal I9 and the junction terminal 22 of resistors 2U and 2i, and the diagonal arm of the second birdge consists of a coil B which forms the second winding of the cross-coil instrument.

Two of the resistors forming symmetrically arranged arms of the double bridge circuit, for example, the resistors I3 and 2i, are composed of a material the resistance of which varies appreciably with temperature in comparison with the temperature effect of the other resistors. Preferably, in order to accentuate the effect, the other resistors are composed of a material which has little or no temperature coefficient of resistance such as maganin or Constantin, for example, or some other suitable material well known to those skilled in the art. The resistors i3 andi may be composed of copper or nickel wire or any other suitable material known to those skilled in the art having a relatively high temperature coeiiicient oi resistance.

For the type of operation desired under ordinary circumstances, it ls preferable to select the dimensions of the electric circuit elements oi' the resistance bridge arms so that the bridge circuits will be balanced at two different temperatures within the desired range of temperature indication. For normal conditions the preferred arrangement is to have one of the bridge circuits balance at a temperature representing 1/5 the desired total scale angle and the other bridge circuit balanced at a temperature representing 4;?, ci the desired total scale angle.

Let it be assumed, for instance, that the bridge consisting of the elements A, Il, I2, i3 and ifi is balanced at a temperature l/5 the way up scale from the minimum temperature to be measured by the apparatus. When this temperature exists no current will flow in the coil A and the direction of the magnetic iiux will be determined wholly by the position of the coil B. The cross-coil instrument comprising the coils A and B is represented schematically in Fig. 5A where the coils A and B are shown mounted at right angles to one another with magnetic axes intersecting and with a transversely magnetized rotor 23 mounted with the axis of rotation passing through the intersection of the magnetic axes of the coils A and B and perpendicular thereto.' It desired. the

windings A and B may each be divided into two coils connected in series and mounted on opposite sides of the rotor 23. The current responsive instrument may be of the type illustrateJ'in Patent No. 2,248,616, granted to Faus, but with four coils and with the opposite coilsl connected in series and in separate circuits to form the Windings'A and B.

As the temperature deviates above or below the value at which zero current iiows in the coil A, the bridge including the coil A will be unbalanced in one direction or the other, and current will flow through the coil A in one direction or the other producing deflection oi the rotor 22 according to the direction or deviation of the temperature. At the assumed temperature V5 of the way up the scale, when the amount of current flowing in the coil A is zero and the position of the rotor 23 is determined entirely by the coil B, the magnetic rotor 28 will take up a position with its poles NS along the magnetic axis oi the coil B represented by the arrow 2l as illustrated in Fig. 5A. vWhen the temperature falls to a minimum, current will now in the coil A and the flux is assumed to be in such a position as to deiiect the rotor 23 to the left to the position represented by the arrow 25. Since the coil B is also carrying current the arrow 25 will be at some position representing the resultant of the uxes of the coils A and B. As the temperature rises to mid scale the rotor 23 will deiiect in the other direction toward a resultant position represented by the arrow 25 half way between the coils A and B. At a temperature represented by the $6 position on the scale the rotor will take the position of the arrow 21 through the magnetic axis of the coil A, since then the bridge l2, I4, 20, 2l is balanced and no current flows through the coil B. At the maximum temperature the rotor will take up a position represented by the arrow 28 beyond the coil A. The angular distance between the maximum and minimum points 25 and 28 will approach degrees.

It will be observed that the currents in the coils A and B each reverse as well as vary in magnitude in accordance with variations in temperature, thus bringing about the long scale angle of the system.

Although the arrangement of Fig. 5 is particularly well adapted for the measurement of temperature it is not limited thereto and may be used also for the measurement of resistance, for example, or to form a remote position indicator. For example, the resistors I 3 and 2l may be replaced by a telemeter transmitter resistor 28, shown in Fig. 5B, having a mid terminal l1 dividing the resistor into two parts, I3' and 2 I corresponding to the resistance arms I3 and 2|. In place oi iixed connections to the ends of the resistor 29 adjustable connections I8 and 22 corresponding to the terminals I8 and 22 of Fig. 5 may be used. The adjustable connections Il' and with temperature.

ample, the bridge arm designated Il".

Il' serve for scale end adjustment. In place of the nxed connection between the resistor M and the junction of the bridge arms It and 2| a movable 'brush I0 is utilized in the arrangement of Pig. 5B. The brush 30 is slidable along the resistor 'la lnresponse to change in an indicationor a position to 'be remotely indicated. For example, the brush It may be connected by a linkage (not shown) to a iloat arm attached to a ilcat in a fuel tank in order to form a remote indicating float gauge with a scale angle about 150 degrees lon g. AIl! a slightly shorter scale angle is sumcient.

a simplified arrangement of Fig. 8 may be employed which utilizes only a single bridge and only one bridge arm, the resistance of which varies with temperature. With this arrangement a scale length of about 120 degrees may be obtained. Any one of thel bridge arms may be composed of a resistance' material which varies in resistance Asin Fig. 5 one oi' the instrument coils A is connected across the con- Jugate terminals of the bridge il and I t. The

second coil of the instrument, however, in this casel designated B', is utilised as an auxiliary winding and is connected in series with a resistor ll across one oi' the arms of the bridge, for ex- The bridge arm It" may have a resistance varying with temperature as inthe case of Fig. 5. However, a slightly greater deflection may be obtained by making the arm Il or the arm l! the temperature variablev resistance arm so as .to produce variations in current ilow in the coil B as well as in the coil A in response to variations in temperature. It will be understood that if the coil were shunted across a resistor included in a constant resistance circuit. it would act merely as a biasing coil and the current therein would not vary in response to variations in temperature.

It willl be understood that the arrangements of I'igs. 5 and 6 lmay also be utilized with a battery having one terminal grounded in order to minviiniiie the number of insulated conductors required. For example, ii' one oi' the terminals of the battery Il is connected to a ground connecuon n, the iowerends or the resistors `n, u, 1|, Il". il" and Il may be grounded at the moet convenient locations instead of being connected by means oi' insulated conductors to the terminal Il. 1

The arrangement oi Pig. 6 is preferably so aci-A justed that the bridge is balanced at the center scale position of the instrument and the resist -ance of the resistor Il is so chosen that the pointer deilects to the ends of the scale atthe temperatures which are to be the maximum and minimum temperatures ofthe range for which the temperature measuring system is to be used.

In the arrangement of Fig. 7, in order to have a highly compact sensitive -arrangement, I employ a main winding A wound from many turns of wire and I employ an auxiliary or control winding B which consists of fewer turns and I connect the winding B in series with the current source il to the bridge il, I2. Il and I I. In thismanner ample current is available for energizing the winding B. since the winding B carries the full bridge cui-reni: except for that carried by a re- 'sistor Il connected in shunt to the winding B lor temperature compensation. The resistor 88 may be made adjustable if desired ior the purpose of adjusting scale length,l since for al nxedl adjustment oi' the resistor the winding B -carries a fixed current, whereas the main windingA carries a reversible current variable in response to variations in temperature. Under normal conditions the resistances are so chosen that the bridge is balanced -at the center scale temperature.

The variable resistance arm il, as in the case o! Pigs. 5 and 6. may be composed of any sultable resistance material having an adequate temperature coemcient of resistance. It may, for ex,

ample. consist of thermometer resistance wire serves to provide indications of temperature and give a wide angle of deiiection of the current rea sponsive instrument is shown in Fig. 8. The ux of the winding B which remains substantially constant is represented by the vertical vector and the ilux oi' the coll A at right angles thereto at a given maximum temperature T1 is represented by the vector Ti. The rotor oi.' the current-responsive instrument takes up an angular position determined by the resultant oi' the vectors A and B, viz: the vector R. The corresponding resultant vector lor the minimum temperature o! the scale is Re. By making the coil A stronger than the coil B it will be observed that a wide angle of denection is obtained. the angular length of the scale being represented by the angle between the vector R and the dotted vector Rr. In the event the temperature varies from Ti to Ta the resultant neld produced by the windings A and B is the resultant of the vectors Ta and B or R', Thus', as the temperature varies the resultant ilux and the rotor position varies between the angular positions o1' R and Rz. With a ilxed amount oi variation in the vector ilux A, changes in B will an'ect the total indicator scale angle.

Therefore the scale angle may be adjusted by adjusting the resistance o! the shunt It to allow lor variations in manufacturing tolerances.

One of the important advantages o! the circuit otFlg;7isthei'actthatonlythewindingA need be highly sensitive as the winding B may be excited by any reasonable amountoi current.

However, if desired the circuit may be rearranged to have the coll B with its compensating shunt and a series resistor shunted around the bridge in which case adjustment of the series resistor would form the adjustment oi' the length oi' scale angle. Also the complete bridge may be shunted by an adjustable resistor for adjusting the current through the coil B to control the scale angle.

The manner in which the circuit of Fig. 'I

vcompensates for variations in ambient temperature will be better understood by ilrst considering the operation in the event that the compensating resistor I) is omitted. It 4will be assumed that all the resistance other than the resistance oi' the coils A and B and the resistance ot the bulb i i are relatively constant and will have negligibletemperature coemcients of resistance. The

resistance oi the series resistor Il tends to swamp out variations in resistance o! the coil B and the current i'lowing through the coil B tends to re-A main constant as the ambient temperature varies. However. the variation .in ambient temperature t5 produces variations in the resistance ot the coil A which is wound of copper wire and, consequently, a deflection of the instrument varies with variations in ambient temperature. On the other hand, when the resistor 33 is connected, variations in ambient temperature will cause vari- -compensation will be obtained by proper selection of the ratios between the reslstances of the elements B and 33 at the average ambient temperature. I have found that indications may be made accurate to a fraction of a per cent over an ambient temperature range of from 50 degrees below zero to 'I0 degrees above zero C.

A current responsive instrument construction, especially well adapted for use with the arrangement of Fig. is illustrated in Figs. l to 4. The apparatus here illustrated comprises a suitable insulating base and connection block 3i supporting a housing or frame 38 composed o! a material such as cast aluminum, for example,

. in which are mounted the windings A and B and a magnetic rotor 31 cooperating with the Velectrlcal windings A and B.

The main `winding A is wound on a separable coil'iorm in order that it may be mounted around the rotor. It may be'divided into a plurality of parts so as to form a winding mechanically divisible into a plurality of winding spools, e. g..

v fourwinding spools carrying mechanically separate coils 31', 33, 33 and 40, as shown in Figs. 3 and 4. These coils correspond to winding A, Figs. 5, 5A, 6 and 7.. The coils 31' to 40 are electrically connected in series, however, by conductors (not shown). For the sake of maximum compactness the coils 31' to' 4l are so formed` and mounted as to illl as nea'rly as possible a circumscribing cylinder represented by the inner' surface of a magnetic shield 4l composed of suitable high permeability material such as Mu metal, for example. nciently narrow, however, to leave space at the sides for thin coils l! and Il which form two mechanically separate parts of the auxiliary winding B, which are also electrically connected Y in series by conductors (not shown). As shown by windingpartsorcoilssoastoobtail'lthemaxi-v mum winding cross-section in eaclnsuch part :without `danger of inadequate mechanical supportor diiilculty from sliding wires encountered' inattempting to wind a coil whichis tapered in thickness or has subnantially diilerent coil thick- ,ness in diilerent parteci the coil. The separability of the winding A also facilitates assemv .bly of the apparatus. Y

The largerinnercoilsn andliarewmmdo'n separable winding'forms which may be thought For single-flange spools N and Il comprising ilanges andll integrdwithhollowcoresor sbcllsllandll lacbctthesbells 'Ihe coils Il and l! are left su!- .asumen I3 and Il is semi-cylindrical in shape so that when the winding forms Il and 45 are iltted together a cylindrical space is provided within the coils to receive the rotor 31. The shells Il and I3 may be composed of a suitable conducting material such as copper, so as to form a damping cup. Each has a projection, only one oi which, Il, is visible, serving to support winding forms or spools Il and l2 carrying the coils 31' and III, respectively. Each of the spools Il and l2 consists of an inner nat rectangular ilange l! and an outer iiange 5I which is a segment of a cylinder with an integral core I! having an opening iitting the projection l0 of the inner winding form M or 4l. Countersunk screw holes Il and threaded holes l1 are provided in the outer and inner winding forms respectively to permit assembly oi the winding A by means of screws,

only one o! which, ll, is shown in Fig. 3. Thel inner flanges 53 oi' the outer spools Il and l2 serve also as outer flanges of the inner spools 44 and 45. y

The parts Il and 43 of the auxiliary winding B are also wound on coil i'orms or. spools 53 which are shown to be thin and slightly curved in order` to fit within the cylindrical surface oi the shield 4| (Fig. 2). The con forms tailor the winding B have long rectangular openings lll and it will. be observed that the ilanges '.40 and of the inner coil forms of the winding A have side projections 8l, oi such dimensions as' tp form a support over which the opening 3l may bentted `when the coil A has been assembled as shown in Fig. 3.

It will be seen that each oi the coil forms $3 for the auxiliary winding B serves also to hold together the projection 3l oi the coil forms oi the main winding A so as to hold this winding in as-` sembled relation as illustrated in Fig. 3. The. en

tire assembly of Fig. 3 is inserted in the Mu metal shield ll of Fig. 2. The coil forms 53 are also heldin place and all parts oi the assembly oi Fig.

3 are held together, by theshicld Il.

For holding the shield 4I within the frame Ill a sub-bridge 62 covering the trame or housing 33 is provided which is secured thereto in any suitable manner as by means of screws 83. An insulating ring M is placed over the assembly of Pig. 3 as shown in Fig. 2, and a spring clip 65, fitting between the top bridge l2 and an insulating ring Il, is provided to hold down the insulator I4 and to hold the assembly of Fig. 3 in place within the shield u.

As illustrated in Figs. 3 and 4 the coil forms u and 4I are constructed with apertures It to provide space for a spindle Il supporting the rotor 31.V The spindle l1 has pivots at the upper and lower ends cooperating with jewel bearings of conventional type and carries a balanced bent pointer il also of conventional type cooperating' with a graduated scale (not shown). It will be understood that suitable openings are provided in the insulator Il and the top bridge 3l to receive the rotor spindle l1. n

Itwillbeobeervedthatapairoiterminalluss' l! is provided for making connections to one o! the windings A and a second pair oi terminal lugs W is provided for making connections to the v may mount approximately atk the position of the screw .88, a ilat plate magnet magnetized in the direction of its thickness, such as shown at N-in Fig. 9 ofthe application of Harold T. Faus. Serial No. 295,597. nled September 19. 1939. and assigned to the same assignee as the presentanplication. Suitable material for such a nat magnet is disclosed also in Patent 2,002,445. granted to Arey and Faus.

It will be observed from Figs. 3 and 4 that the winding B is composed of coils which are quite narrow in comparison with the'coils comprising the winding A. Accordingly the winding'B produces a relatively narrow magnetic field act- A ing upon the rotor I1. The rotor 31 is composed of high-coercive-force, exceedingly light. transversely magnetized material composed of a mixture of sintered oxides. such as described in Patent No. 2.248.618. granted to Faus. The rotor I1 is also similar in shape'to the aforesaid rotor described in the above patent, except that it is ilattened on the sides 12, the sides being par- -allel to the line of magnetization Il passing through the poles N and B of the rotor 81. Fig. 4 illustrates the pointer 9| and the rotor I1 in the position which corresponds to the center scale position of the instrument.

In this position the rotor 31 has its line of magnetization 'Il passing through the coils 42 and 4I forming the winding B, thus coinciding with the magnetic axis'of the winding B. Owing to the narrowness of the magnetic neld of the coil B and the additional fact that the rotor l1 is flattened on the sides so that it also has a narrow magnetic field. the component of force in the direction through the coils 42 and 4l of thewinding B acting upon the rotor II'is greatest when the rotor I1 is in the center coil position illustrated in Fig. -i and least when the rotor 81 is in either of the endl scale positions approaching 90l degrees in either direction from the position ily lustrated in Fig. 4. Thus, the arrangement overcomes end compression ofthe scale. y

'I'he advantage obtained by the narrow field arrangement Just described in connection with the rotor I1 and the auxiliary winding 1B will be better understood by nrst considering the action of an instrument in which the main coil A and the cross coil B act with the same eiIect on the rotor and the rotor is symmetrical with respect toits axis of rotation. Under these circumstances the force of either coil tends to vary.

" sinusoidally with the angular position of the rotor. Deiieetion is produced in such instruments, however, by variation in held strength of at least one of the coils. Since in the circuit or Fig. 7 the current and neld strengths of the winding B are held substantially constant. deection is produced by variations in strength of the flux produced by the winding A.

In the vector diagram of Fig. 9 the vertical vector B represents the iluxproduced by the coil B. This vector represents the component of force actingupon they rotor I1 in a direction through the coils I2 and Il of the winding B. ,The current and flux in the winding A is assumed to be varied in iive successive increments as represented by the horizontal vectors Ao toAs. For

these six diiIerent values of current in the winding Arepresented in Fig. 9. there will be six different resulting tlux directions represented by the resultant vectors Ro, R1. R2, Ra, R4 and Rs.` It will be seen, however. that the angular spacing between the vectors Rs to Rs is not uniform. Consequently. a non-uniform scale is obtained although the eiIect in the coil A was assumed to be uniform. Such a compression of the end scale region and expansion of the -mid scale region may be desired in some cases andthe main expanded region may be varied by balancing the bridge of Fig. 'I at a'diiIerent point from the center scale Vif desired. However. ordinarily a linear angular deilection is desired.

Referring again to Fig. 9 and recalling that as described in connection with Fig. 4 the instrument there illustrated does not have a uniform ycross force acting uponl the rotor Il for diiIerent angular positions thereof notwithstanding constancy of current in the winding B, it will be seen that with this type of instrument the vector B no longer represents the component of force acting in a direction through the magnetic axis of the windingB. On the contrary. when the rotor is inthe center scale position this component of force. the cross force, as it may be called for convenience, is at a maximum value B represented by the dotted vector in Fig. 9.

and as the rotor deilects toward the end positions of the scale, thecross force falls to a minimum value which will be assumed to be equal to the vector B. The action for scale end positionswhen the flux of the coil A equals either Ao or As is unchanged. However, when the ux of the coil A changes to the value A1 the component of force 'acting crosswise has increased to Bi and the resultant force is R'i. Then when 'theiiux of the-winding A reaches a value A:

the cross component of force rises-to the value B'z and the resultant ilux is represented by the vector Rz. In a similar manner other values f of resultant aux R': and R'i are obtained. It

variations are possible and I aim therefore to t t cover all such modifications and variations as fall within the scope of my invention which are defined in the appended claims.

,What I claim as new and desire to secure by Letters `Patent of the United States is:

I. A compact current-responsive device comprising a cylindrical enclosure. a current conducting winding fitted closely into said enclosure and a magnetic rotor mounted within the winding substantially concentrically with said cylindrical enclosure with an axis of rotation substantially coincident with the axis of the cylindrical enclosure and magnetized transversely to such axis, said winding comprising'four winding forms and four coils woundthereon, the winding forms having cores which are substantially segments of a cylinder and the coils being built up to form a winding of stepped cross-section largely iilling the said cylindrical enclosure, the cores being hollow and the four coils being iitted together with coincident magnetic axes transverse to and substantially intersecting the axis of rotation of the said rotor whereby the Winding forms when tted together form a cylindrical recess for the said rotor.

2. A compact double-coil current-responsive device comprising a cylindrical enclosure, a main current conducting winding, an auxiliary or cross eld winding iitted closely into said enclosure, and a magnetic rotor mounted within the main winding substantially concentrically with said cylindrical enclosure with an axis of rotation substantially coincident with the cylindrical axis of the enclosure, and magnetized transversely to such axis, said main Winding comprising a winding form with a. hollow cylindrical shell forming a recess for the rotor, and flanges extending from the shell defining four coil areas with coil planes parallel to each other and to the cylindrical axis of the shell, and coils wound into said four coil areas to form a winding with a magnetic axis transverse to and substantially intersecting the cylindrical axis and with a cross-section having a circular center and a stepped outline to occupy efllciently the space between the cylindrical core and the said cylindrical enclosure while retaining adequate support for the layers of winding, and the auxiliary winding comprising a pair oi coils each occupying the space between one of the edges of the coils oi the main winding and an adjacent surface of the cylindrical enclosure.

3. A narrow cross-field current ratio responsive instrument, comprising a rotatably mounted rotor magnetized transverse to its axis of rotation having a greater dimension in the direction along its line of magnetization than in a line transverse to said line and to said axis of rotation, and a eld structure comprising a main winding .avins a magnetic axis substantially intersecting the axis of rotation of the rotor and substantially perpendicular thereto and an auxiliary or crossiield winding having a magnetic axis substantially perpendicular to that of the main winding and to the axis of rotation of the rotor, said auxiliary winding producing a ileld acting on the rotor which is-relatively narrow in comparison with the width ofthe eld produced by the main iield winding acting on the rotor, said instrument having a scale with an intermediate point corresponding to the angularposition of the rotor with andtotheaxisofrotaonoftherotonsaid.

auxiliary winding producing a neld acting on the rotor which is relatively narrow in comparison withtheileldothemain'windingactingonthe rotor, said instrument havingsaV scale with an intermediate point corresponding to the angular position of the rotor with its line of tion passing through the auxiliary winding whereby the attraction of said auxiliary winding for the rotor is greatest with the rotor in the said intermediate scale position and least with the rotor in the end scale positions.

5. A narrow cross-held current ratio responsive instrument, comprising a iieid structure and l rotatably mounted rotor magnetized in the direction of a line transverse to its axis of rotation, having a cross-section substantially circular but with two nattened sides so as to provide greater dimension in the direction along the line oi magnetization than in a line transverse to said line and to said axis of rotation, said neld structure comprising a main winding having a magnetic axis substantially intersecting the axis of rotation of the rotor and substantially perpendicular thereto and an auxiliary or cross-field winding having a magnetic axis substantially perpendicular to that of the main winding and to the axis of rotation of the rotor, said instrument having a scale with an intermediate point corresponding to the angular position of the rotor with its lines of magnetization passing through the auxiliary winding whereby the attraction of said auxiliary winding for the rotor `is greatest with the rotor in the said intermediate scale position and least with the rotor in the end scale positions.

6. A compact current-responsive device comprising a cylindrical enclosure, a current conducting winding fitted closely into said enclosure and a magnetic rotor mounted within the winding substantially concentrically with said cylindrical enclosure with an axis of rotation substantially coincident with the axis of the cylindrical enclosure and magnetized transversely to such axis, said winding comprising a plurality oi winding forms and a plurality of coils wound thereon, the winding forms having cores which are substantially segments of a cylinder, the coils being built up to form a winding of stepped crosssection largely filling the said cylindrical enclosure, the cores being hollow, and the coils being ntted together with coincident magnetic axes trans-V verse to and substantially intersecting the axis of rotation of the said rotor whereby the winding forms when iltted together form a cylindrical recess for the said rotor.

7. A compact current-responsive device oomprising a cylindrical enclosure, a. current conducting winding ntted closely into said enclosure and a magnetic rotor mounted within the winding substantially concentrically with said cylindrical enclosure with an axis ot rotation substantially coincident with the axis oi the cylindrical cnclosureandmagnetizedtransverselytomchaxil. said winding comprising s winding form split to permit opening for reception of the magnetic rotin-andeoilswoundtheremthscoilsbeing builtuptoiormawindinglargelynllingthssdd cylindrical enclosure and having magnetic axes transversetosaidaxisoi rotation.

Y 8. A compact current-responsive device comprlsingacylindrical enclosure, acurrcnt conductingwindingnttedcloselyintcsaidenclosm'e andamagneticrotormountedwithinthowinding substantially ooncentrically with said cylindrlcalenclosurewithanaxisoi rotntionsubstantislly coincident with the axis of the cylindricalenclosureandmagnetisedtransverselyto such axis, said winding comprising a winding form and electrically conducting wire wound thereon'thewindingfonnbelnghollowwithn vYrotoxrecessthereinsubstantiallycylixmrirllcnlwith n-cylindricll nxls'lullhntlnlb coinddent 'mi netic axis transverse to and substantially interthe axis of the said cylindrical enclosure, the wire being wound around said recess with a magsecting the cylindrical axes and the wire largely filling the space between said cylindricalrecess and the remainder of 'said cylindricalenclosure. 9. A compact double-coil current-responsive ,ases

device comprising a cylindrical enclosure, a main y ly to such axis, said main winding comprising a winding form with a hollow cylindrical shell forming a recess for the rotor, and vflanges extending from the shell defining a plurality lof coil areas with coil planes parallel to each other and to the cylindrical axis of the shell and coils wound into said coil areas" to form a winding with a magnetic axis transverse to and substantially intersecting the cylindrical axis, and with a cross-section having` a circular center and a stepped outline to. occupy emciently the space between thev cylindrical core and the said cylindrical enclosure while retaining adequate supss y 7 port for the layers of winding. .and the auxiliary winding comprising a pair oi' coils each occupying the space between one of the edges of the coils of the main winding and an adjacent surface of the cylindrical enclosure.

i0. A compact double-coil current-responsive device comprising a cylindrical enclosure, a main current` conducting winding, an auxiliary or cross-field winding iitted closely into said enclosure, and a magnetic rotor mounted within the main winding substantially concentrically with said cylindrical enclosure with an axis of rotation substantially coincident with the cylindrical axis of the enclosure. and magnetized transversely to such axis, .said main winding comprising a winding form with a hollow shell having a substantially circular center and an outline approaching in shape a flattened circle in order to occupy eilciently the space between the cylindrical core and the cylindrical enclosure, and the auxiliary winding occupying the space between the edge of the main winding forming the flattened side of said circular out-l line and an.adjacent surface of the cylindricalenclosure whereby the cylindrical enclosure is efliciently occupied by electricaizwinding material.

FREDERICK R.. BIAS. 

